I think I've found the answer. NT is generally okay with MSDN.

I installed a fresh, scratch NT SP5. I find that the new MSDN carries with it on the CDs not only NT SP6a (so I didn't have to go & get it to upgrade), but also the new MS Installer version, and IE6, as well as the library and .NET stuff. Took about 5 reboots, but all is installed and working.

I'm fairly sure the culprit is McAfee 4.5.1, but no one here can disable it for installs as the password is unknown to everyone, apparently. But we were noticing on the Perf Mon that the new McAfee version appeared to be interfering with some apps, causing flickering, interrupts, and spikes.

Since the MSDN install went fine without McAfee (well almost fine, I got a Blue Death once on CD3, but restarted and it finished installing fine), that's probably the problem, as someone suggested earlier. The evil McAfee 4.5.1, at least it's evil until someone can find a password so we can disable it when needed.

Now that it's working, after all this, I'm not sure I like the new MSDN format. It's quite different, for one thing - and there isn't any longer a cohesive KB that I can find, it's scattered among other search headers, unless I'm missing something.